Income Taxes (Narrative) (Details) - USD ($)		12 Months Ended
	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Statutory Federal Income Tax Rate		35.00%
Reduction in net deferred tax assets including valuation allowance		$ 10,700,000
Valuation allowance		790,000	$ 650,000	$ 500,000
Change in Valuation Allowance		100,000
Unrecognized tax benefits		564,000	$ 850,000	$ 0
Idaho [Member]
Income Taxes [Line Items]
Investment Tax Credits		$ 3,100,000
Earliest Tax Year [Member] | Idaho [Member]
Income Taxes [Line Items]
Idaho Investment Tax Credits expiration year		2019
Latest Tax Year [Member] | Idaho [Member]
Income Taxes [Line Items]
Idaho Investment Tax Credits expiration year		2031
Federal [Member]
Income Taxes [Line Items]
Operating Loss Carryforwards		$ 0
State and Local [Member]
Income Taxes [Line Items]
Operating Loss and Capital Loss Carryforwards		$ 1,200,000
State and Local [Member] | Earliest Tax Year [Member]
Income Taxes [Line Items]
Operating Loss and Capital Loss expiration year		2021
State and Local [Member] | Latest Tax Year [Member]
Income Taxes [Line Items]
Operating Loss and Capital Loss expiration year		2030
Subsequent Event [Member]
Income Taxes [Line Items]
Statutory Federal Income Tax Rate	21.00%